Addressing the U.N. Security Council’s periodic Middle East debate, Ban Ki-moon also urged both sides to act now “to prevent the two-state solution from slipping away forever.” He condemned rocket fire from armed groups in Gaza into Israel but focused his strongest comments on Israel’s settlement-building.

“As oppressed peoples have demonstrated throughout the ages, it is human nature to react to occupation,” the U.N. chief said.

Israel has occupied the West Bank, East Jerusalem and other Palestinian territories since the Six Day War in 1967. Palestinians demand the territory as part of their future state. However, Israeli settlements constructed on seized lands have hindered peace negotiations and the formation of a viable Palestinian state.

All Israeli settlements are illegal under international law. Specifically, U.N. Security Council Resolution 446 states: “The policy and practices of Israel in establishing settlements in the Palestinian and other Arab territories occupied since 1967 have no legal validity and constitute a serious obstruction to achieving a comprehensive, just and lasting peace in the Middle East.”

More than 500,000 Israelis live in more than 200 Jewish-only settlements and unofficial outposts — which are communities unrecognized or serviced by the Israeli government — in the West Bank and East Jerusalem.

Last week, Israel approved the seizure of some 380 acres of Palestinian land in the West Bank to further expand settlements near Jericho.

The last four months have seen an increase in violence that has killed at least 149 Palestinians and 25 Israelis. Israel blames the violence on Palestinian incitement. Palestinians say the attacks stem from frustration at nearly five decades of Israeli military rule.

Israeli Prime Minister Benjamin Netanyahu on Tuesday said Ban’s comments “give a tail wind to terrorism,” and he said the U.N. “long ago lost its neutrality and its moral strength.”

Palestinian Ambassador Riyad Mansour later told reporters that all 15 council members acknowledged that Israel’s settlement building is “the main obstacle to any meaningful political process,” and he said the Palestinians are meeting with all council members to assess their readiness to act this year.

French Ambassador Francois Delattre said the international community should create a “specific and credible political horizon” for a solution to the tensions in the region.

Chinese Ambassador Liu Jieyi said Israel should take the lead in calming tensions, and he said the Security Council “should seriously consider the question of providing international protection to the Palestinian people.” He gave no details, but Mansour said new council member Egypt would take the lead in exploring that issue.

The comments by Ban and others came after Netanyahu this week said his government is committed to West Bank settlements. Ban said he was “deeply troubled” by new reports that Israel’s government has approved plans for more than 150 new homes in settlements in the West Bank.

U.S. Ambassador Samantha Power told the council that the United States “strongly opposes settlement activity” but added that “settlement activity can never in itself be an excuse for violence.”